Wire, rod, stick, and the like, with or without fluxing agent for welding applications

ABSTRACT

An improved wire, rod, stick, and the like to be stored, packaged, transported, and fed into welding apparatus is manufactured so that the ultimate alloying stage is performed when used as filler material, or consumable electrode during welding operation. The wire, rod, stick, according to the invention, which may be with or without fluxing agent, is obtained by selecting constituents in relation to a desired alloy system, mixing the selected constituents, and forming a wire, rod or stick cold working, or by extrusion, the alloy system being obtained at the ultimate welding step with the intermediary wire, rod or stick.

BACKGROUND OF THE INVENTION

The invention relates to a welding wire, rod, stick, or the like, ofnovel microstructural configuration, and to techniques for itsmanufacture.

It is known that by extrusion, rolling or squeezing, and more generallyby hot or cold working, two metals of the same or different kind, can bejoined together. It is also known that particulated matter can becompacted under pressure so as to become a unitary mass or body.

The present invention essentially relates to a novel microstructuralconfiguration for a filler wire, rod, or stick typically used in weldingoperations. It consists of an elongated member of material of a preciseand required composition which is melted by the applied heat in thecourse of the welding operation so that a bead of molten material isprogressively yielded to fill the gap along the welding line. Threefactors are of importance for such filler materials.

(1) The filler material must have a precise chemical composition inorder to properly unite the two parts of the workpiece to be welded andform a seam when consumed.

(2) The material melted by the welding heat source must be a metal alloyof precise composition and structure.

(3) The filler wire must have the required cross-section, and be of alength sufficient to be fed regularly by the operator and supply thedesired amount of filler along the seam. A correlative requirement isthat the wire, rod, or stick have sufficient mechanical strength andductibility to be packed, or wound, stored, transported andautomatically fed by the welding apparatus.

In order to solve this problem, the prior art in the context of a metalcomposition has taken two avenues: metallurgical or mechanical alloying.

Forming a rod, wire or stick by mechanical alloying consists in buildinga metal sheath around a core of particulated alloy by continuous rollingor in forming a ceramic coating with such particulated alloy by coldworking or by extrusion around a core of wire.

Metallurgical alloying involves alloying in the initial melting stage toobtain the desired metal composition. The alloy thus formed is then castinto an ingot, and the ingot is hot-worked to form the rod. An ultimatecold-working step combined with annealing changes the rod into a wire.It is clear that the mechanical and metallurgical methods are complexand costly methods of fabricating welding filler wires.

The object of the present invention is to provide a simpler, lessexpensive, wire, rod and/or stick suitable for filler applications inwelding processes.

The filler material, for certain welding applications requiring theaddition of a flux to prevent oxidation and other chemical contaminationat the welding seam, the wire, rod, stick, or the like according to thepresent invention may be a composite material including a fluxing agent.

It is known from U.S. Pat. No. 1,972,463 to make rods or wirescontaining the fluxing agent in a finely-dispersed state throughout thematerial. To this effect, mixtures of powdered metal and fluxing agentare sintered in suitable molds to be brought into the form of rods orwires for welding application. Metal powder is obtained from metalcarbonyl and sintering is performed on the metal powder with thefinely-divided flux by means of heat or mechanical pressure, or both, toform the wire without a melting operation. This patent merely revealsthe problems encountered when a fluxing agent is added, since the agentshould not melt at the early stage of forming the rod, or wire, and theparticles of agent should be intimately embedded in what should be a rodor wire. Still, the production of such rod, or wire by merelyagglomerating together under pressure a mixture of particulatedmaterials, will not yield a high density composite metalic structurehaving on the one hand the required mechanical quality to become, as awelding wire, or rod a staple article, nor which can be easily fed in anautomatic welding machine of the marketplace, nor which can beidentified by its chemical composition and final alloy microstructure(e.g. after being consumed in the welding process). For these reasons,the prior art does not teach or suggest the filler wire, rod, stick, andthe like, with or without fluxing agent, according to the presentinvention.

SUMMARY OF THE INVENTION

According to the present invention, a wire, rod, or stick, with orwithout fluxing agent, for a welding filler material is manufactured andformed without any alloying step. The required alloying step isperformed in situ, e.g., in the molten pool during the welding operationwhere the filler material is being actually consumed. More specifically,the method according to the present invention includes the steps ofselecting constituents of the wire, rod or stick in particulated form,blending such constituents to form a proportionate mixture thereof andcompacting such mixture with sufficient mechanical pressure to form awire, rod or stick of sufficient mechanical strength and flexibility tomake it a welding filler.

It is understood that the selected, blended and compacted constituentsin particulated form are not necessarily made of pure metal. They may bemade of metal alloy. They may include two or more metals, two or morealloys, at least one metal with at least one alloy. The particulatedconstituents need not be all metals or alloys. The object being toprepare under mechanical pressure a composite body which will ultimatelyform a true alloy in the molten weld pool. Constituents in particulatedform may be added as required to obtain the desired alloy system for thebeads in the welding seam. For instance, an aluminum-silicon system maybe intended. In such case, silicon in particulated form and with therequired proportion will be added and mixed with particulated aluminumand then formed into a wire, rod, or stick.

It is known from U.S. Pat. No. 2,659,133 to form a composite metal bodyfrom a mixture of two or more particulate metals, such as magnesium andaluminum, and by the application of heat and pressure by extrusion toobtain a bar consisting of elongated particles and which exhibitsmechanical properties somewhat similar to those of a similar alloyproduced by conventional casting and fabrication techniques. p It isalso known from U.S. Pat. No. 1,323,623 to compress fine particles of asingle pure metal to form a coherent heavy wire and then to heat anddraw such heavy wire in order to reduce it under heat to a densemetallic state. Such coarse wire is then drawn into a fine wire whichwill serve as a wire filament for incandescent lamp filaments. U.S. Pat.No. 2,651,952 also shows compressing and extruding powdered metal toform a continuous rod which is thereafter sintered into a rigid but notfully dense structure.

It is further shown by U.S. Pat. No. 2,708,770 how to make ingot sticksfrom consumable electrodes which are in sponge or powder form throughcompacting followed by arc melting to form the ingot.

In all of the aforementioned patent references, when extrusion orcompacting is used, this is merely an additional or intermediary stepwhich precedes or follows heat treatment. In none of these references isit taught to manufacture a welding filler obtained without heattreatment which at such stage can be packed, wound, stored, transportedand/or marketed and which ultimately will yield an intended alloymicrostructure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in block diagram a mode of implementation of themethod according to the present invention;

FIG. 2 is a photographic view of the internal grain structure of analloy filler wire of the prior art involving 5% silicon with the balancealuminum;

FIG. 3 is a photographic view of the structure of the weld metalobtained when using the filler wire of FIG. 2;

FIG. 4 shows the internal grain structure of a welding filler wire of 5%silicon with the balance aluminum according to the invention; and

FIG. 5 is a photographic view of the structure of a weld bead obtainedduring welding utilizing the welding filler wire according to theinvention shown in FIG. 4.

PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 shows schematically the process which can be used to implementthe method according to the present invention. Two hoppers 1 and 2containing particulated constituents A and B, respectively, are feeding,through corresponding feeding lines 3, 4, a blender 5. Blender 5 feedsthrough line 6 to, for example, an extruder 7 which provides at theoutput a continuous rod, or wire 8 having the proper overallcharacteristics to make it suitable for sale on the market and that canbe used directly as a filler material in welding operations. The outputwire or rod is cut by a shear to sever it to the required lengths. It isalso possible to wind up the continuous wire around a reel (not shown)for storage and transportation, and that can be fed automatically by awelding apparatus.

Referring again to FIG. 1, the combination of a blender such as 5 andand extruder such as 7 is well known. Any type of blender and extrudercan be used. Instead of an extruder, a rolling machine is applicable.Any means for applying sufficient pressure to the output blend of line 6to comform it to the intended cross-sectional dimension of the rod, orwire 8 while compacting and deforming it sufficiently to form producthaving high integrity, can be used. For instance, the apparatus shown inU.S. Pat. No. 4,041,595, 3,922,898, and 3,911,705 of William G. Voorhesor the apparatus shown in U.S. Pat. No. 3,765,216 of Derek Green can beused for implementing the method according to the present invention.Reference should be had also to Wire Technology Nov. 12, 1976, pages23-25.

In the illustrative example of FIG. 1, particulate A is aluminum and Bis silicon, the proportion being 5% of silicon. FIG. 2 shows themicrographic representation of a conventionally manufactured filler wireof aluminum 5% silicon alloy. FIG. 3 shows how the composite heattreated alloy of FIG. 2 has been transformed by a quality weldingoperation. The alloy structure of FIG. 3 represent the final state ofthe alloy in the welding seam when the welded parts are united. Inaccordance with the present invention, the same final metallurgicalstage is to be reached after welding with a wire, rod, stick or the likeof filler material which has received without the application of heatsufficient mechanical qualities to be stored, packed, wound,transported, and fed as a consumable electrode or as a filler wire thatcan be sold in the open market. FIG. 4 shows the grain structure of sucha wire, rod, obtained in accordance with the invention. In contrast tothe grain structure of FIG. 2, the silicon particles are coarser andalloying has not taken place yet.

The mechanical characteristics of the filler wire of the Al-Si typeshown in FIG. 4 compared with the characteristics of the conventionallymanufactured alloy of the same type shown by FIG. 2, are as follows:

    ______________________________________                                                    (.2% Offset)                                                                              Ultimate                                              Invention   Offset      Tensile                                               FIG. 4      Strength    Strength   Elongation                                 (diameter .073)                                                                           (PSI)       (PSI)      (%)                                        ______________________________________                                        Sample #1   10,900      15,900     18                                         Sample #2   11,250      16,200     21                                         Sample #3   10,900      16,100     19                                         Prior Art                                                                     (FIG. 2)                                                                      (diameter .062)                                                               Sample #1               35,990     3                                          Sample #2               33,670     5                                          Sample #3               33,670     4                                          ______________________________________                                    

It is clear that the alloying method of the prior art for the same basicmetallurgical composition (Aluminum - 5% Silicon) permits higher tensilestrengths, but has the result of the heat treatment invested at thestart. In contrast, the wire according to the invention represents asubstantial saving, with adequate mechanical properties even with thelack of heat treatment. A softer but ductile wire is obtained having allthe necessary requirements.

The mechanical structure of the filler wire, rod, or stick according tothe invention appears to be quite sufficient for storage, packing,transportation, and weldfeed. Therefore, there is no need to pay thehigher cost involved in the conventional manufacture of such fillermaterials. More generally, the filler wire, rod, or stick, according tothe invention compares favorably with conventional welding fillermaterial.

FIG. 4 shows the microscopic structure of a cross-section of the Al-5%Si filler wire made according to the present invention. The structureconsists of discrete, approximately spherical particles of siliconuniformly distributed in an aluminum matrix.

FIG. 5 shows the microscopic structure of a sample taken from a beadobtained from consumption of the welding filler wire according to thepresent invention. Assuming that the aluminum-5% silicon composition ofthe disclosed filler wire 9 is quantitatively comparable to the basiccontent of the conventional alloy wire of FIG. 2, the resulting weldbead structures can be compared (FIG. 3 and FIG. 5). Experience hasproved that the alloy derived from the disclosed filler wire when it ismelted in the welding operation results in a solidified structuresimilar to that achieved using a conventionally manufactured fillerwire.

From a comparison of FIG. 3 and FIG. 5, it is clear that the ultimatealloying step by melting during welding yields the very same alloymicrostructure as would be obtained by the detour of preheat treatmentbefore or during forming of the wire, rod or stick in the prior art. Thesame quality welding has been obtained by a different route. The methodaccording to the present invention is less costly, it does notsubstantially lose anything in producing a wire, rod, or stick which isa staple article. The filler rod or consumable electrode, so obtainedcan be identified in terms of the final alloy composition, or particularwelding oeration, with or without fluxing agent.

By the same method, fluxing agent in particulated form may be added,mixed and compacted with the constituents of the intended weldingfiller. It has been determined that such addition of fluxing agent willnot impair the quality of the alloy obtained at the welding stage, andwill provide during welding the improved effectiveness usually achievedwhen an appropriate fluxing agent is present during welding.

What is claimed is:
 1. A consumable electrode of predetermined lengthand cross-section obtained as a staple article by the followingsteps:selecting particulated metals, said metals being constituents ofan alloy system suitable for a predetermined welding process; adding andblending said particulated metals in proportions defined by said alloysystem; extruding and conforming the blended particulated metals to saidpredetermined cross-section and for said predetermined length under amechanical pressure sufficient to generate a bendable composite unitarybody having definite mechanical characteristics in several directionsincluding mechanical strength and ductility; said steps being short ofany heating process and of any chemical union of any of the particulatedmetals whereby said composite body is obtained as a staple article ofsaid length and cross-section which is susceptible when used as aconsumable electrode of yielding in situ under said welding process analloy conforming to said alloy system.
 2. The consumable electrode ofclaim 1 with at least one fluxing agent in particulated form being addedand blended with said particulated metals at said adding and blendingstep.
 3. The consumable electrode of claim 1 with said metalconstituents including at least 5% silicon in powder form, the restbeing aluminum in particulated form.